There are many possibilities for using absorption of light for processing a work-piece, in particular by introducing localized modifications into the work-piece. The so-called volume absorption, i.e., an absorption that is not limited to the surface, opens the possibility to process brittle-hard materials that are essentially transparent for the laser beam. Generally, volume absorption benefits from a kind of nonlinear absorption, at which an interaction with the material takes place only at a material dependent (threshold) intensity.